Collapsible and re-expandable prosthetic heart valve cuff designs and complementary technological applications

ABSTRACT

A prosthetic heart valve is provided with a cuff having features which promote sealing with the native tissues even where the native tissues are irregular. The cuff may include a portion adapted to bear on the LVOT when the valve is implanted in a native aortic valve. The valve may include elements for biasing the cuff outwardly with respect to the stent body when the stent body is in an expanded condition. The cuff may have portions of different thickness distributed around the circumference of the valve in a pattern matching the shape of the opening defined by the native tissue. All or part of the cuff may be movable relative to the stent during implantation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 12/737,256 filed Dec. 22, 2010, which is a national phase entryunder 35 U.S.C. §371 of International Application No. PCT/US2009/004094filed Jul. 15, 2009, published in English, which claims the benefit ofthe filing date of U.S. Provisional Patent Application No. 61/134,995filed Jul. 15, 2008, the disclosures of all of which are herebyincorporated herein by reference.

FIELD OF THE INVENTION

The present invention is directed to prosthetic heart valves forreplacement of native heart valves, to components for use in suchprosthetic heart valves, and to methods of treating patients with suchprosthetic heart valves.

BACKGROUND OF THE INVENTION

Certain prosthetic heart valves incorporate an expandable stent body andvalve elements such as prosthetic valve leaflets mounted to the stentbody. The prosthetic valve may also include a cuff including one or morelayers of materials such as fabric or animal tissue. Valves of this typemay be implanted in the heart by advancing the valve into the body ofthe patient with the stent body and cuff in a collapsed condition inwhich the stent body and cuff have a relatively small diameter. Once thevalve is positioned at the desired implantation site, the stent body isbrought to an expanded condition in which a portion of the stent bodyhas a generally tubular shape. This portion engages the surroundingnative tissue and holds the valve in place. The cuff forms a liningcovering all or part of the tubular stent body. The valve acts as afunctional replacement for the diseased native valve. Thus, the valveelements inside the stent body permit blood flow in the antegradedirection but substantially block flow in the opposite, retrogradedirection. For example, a prosthetic valve may be advanced to a sitewithin a diseased native aortic valve percutaneously through thearterial system and into the aorta to the native aortic valve. In atransapical placement, a prosthetic valve may be advanced through anincision in the apex of the heart and through the left ventricle to thenative aortic valve. Other approaches through other access sites can beused. Once the prosthetic valve is in place, it permits flow from theleft ventricle into the aorta when the left ventricle contracts duringsystole, but substantially blocks retrograde flow from the aorta intothe left ventricle during diastole.

There are significant challenges in design of an expandable valve. Forexample, the valve desirably can be collapsed to a relatively smalldiameter to facilitate advancement into the body. This imposessignificant limitations on the design of the cuff as, for example, thethickness of the material which can be incorporated in the cuff.However, the stent body must be capable of expanding to an operative,expanded condition in which the stent body securely engages thesurrounding native tissues to hold the valve in place. The stent bodyand the cuff carried on the stent body should form a good seal with thesurrounding native tissues to prevent leakage around the outside of theprosthetic valve, commonly referred to as perivalvular leakage. However,the stent body and cuff should not apply excessive forces to the annulusof the native valve. Excessive forces on the annulus of the nativeaortic valve can disrupt the electrical conduction system of the heartand also can impair the functioning of the mitral valve. These issuesare complicated by the fact that the diseased native valve leaflets andother diseased tissues may present an implantation site which isirregular. For example, patients with calcified or stenotic aorticvalves may not be treated well with the current collapsible valvedesigns, and may encounter problems such as (1) perivalvular leakage (PVleak), (2) valve migration, (3) mitral valve impingement, (4) conductionsystem disruption, etc., all of which can lead to adverse clinicaloutcomes. To reduce these adverse events, the optimal valve would sealand anchor adequately without the need for excessive radial force thatcould harm nearby anatomy and physiology.

Numerous prosthetic valve and stent body designs have been proposed.However, despite all of the attention devoted to such designs, stillfurther improvements would be desirable.

BRIEF SUMMARY OF THE INVENTION

One aspect of the present invention provides a prosthetic heart valve.The valve according to this aspect of the invention desirably includes astent body having a generally tubular annulus region. The stent body,and particularly the annulus region, has a proximal-to-distal axis. Thestent body has a radially collapsed condition and a radially expandedcondition, the annulus region increasing in diameter during transitionfrom the radially collapsed condition to the radially expandedcondition. The valve according to this aspect of the invention desirablyincludes one or more prosthetic valve elements as, for example,prosthetic valve leaflets. The prosthetic valve elements are mounted tothe stent body and are operative to allow flow in the antegradedirection through the annulus region but to substantially block flow inthe retrograde direction through the annulus region when the stent bodyis in the radially expanded condition.

The valve according to this aspect of the invention most preferablyincludes a cuff secured to the stent body. The cuff may include a firstcuff portion covering at least a portion of the annulus region fordisposition at said native valve annulus, the first cuff portion havinga first diameter when the annulus region is in the radially expandedcondition. In this aspect of the invention, the cuff desirably alsoincludes a second cuff portion proximal to the first cuff portion, thesecond cuff portion having a second diameter when the annulus region isin the radially expanded condition, the second diameter being greaterthan the first diameter. The second cuff portion preferably is adaptedfor engagement with native tissue proximal to the native valve annulus.For example, where the prosthetic valve is implanted in a diseasednative aortic valve, the second cuff portion may engage the leftventricular outflow tract or LVOT.

A further aspect of the invention provides a prosthetic valve which mayhave a stent body and valve element as discussed above. A valveaccording to this aspect of the invention desirably includes a cuffsecured to the stent body and surrounding the annulus region, the cuffhaving one or more pleats adapted to collapse in axial directions andexpand in radial directions upon transition of the stent body from theradially collapsed condition to the radially expanded condition. Asfurther discussed below, the pleats can promote effective sealing withthe surrounding native structures.

A valve according to yet another aspect of the invention desirablyincludes a stent body with a generally tubular annulus region having aproximal-to-distal axis, and desirably also includes prosthetic valveelements mounted to the stent body as discussed above. The valveaccording to this aspect of the invention most preferably has a cuffsecured to the stent body and surrounding the annulus region; and alsohas one or more biasing elements separate from the cuff. The biasingelements are mechanically connected to the stent body and to the cuff,and are adapted to bias at least a portion of the cuff outwardly withrespect to the stent body. Merely by way of example, the biasingelements may include springs formed separately from the stent body orintegral with the stent body, and may also include a hygroscopic,water-swellable material disposed between the cuff and the stent body.By biasing the cuff outwardly from the stent body, the biasing elementstend to promote intimate engagement between the cuff and the surroundingtissues, even where the surrounding tissues are irregular.

A still further aspect of the invention provides a prosthetic valvewhich includes an expansible stent body and valve elements, and whichalso includes a cuff secured to the stent body. The cuff desirably has amobile portion movable in an axial direction with respect to the stentbody so that when the stent body is in the radially collapsed condition,the mobile portion of the cuff is axially offset from the annulus regionof the stent body. Most preferably, the mobile portion of the cuff canbe displaced to an operative position in which the mobile portion of thecuff extends around the annulus section. For example, the cuff may havea generally tubular wall with a fixed end attached to the stent body anda free end projecting axially away from the annulus section when thestent body is in the radially collapsed condition. In this arrangement,the mobile portion of the cuff includes the free end of the tubularwall. The tubular wall desirably is constructed and arranged so that thetubular wall may be turned inside-out so as to bring the free end of thetubular wall into the operative position. Thus, the free end of thetubular wall extends around the annulus region when the cuff is in theoperative position.

Still another aspect of the invention provides a valve with a stent bodyand valve elements. The valve further includes a cuff having pocketswith open sides. The open sides face in an axial direction, such as inthe distal direction, so that flow of blood will tend to expand thepockets and bring the cuff into tighter engagement with the surroundingtissues.

Yet another aspect of the invention provides a valve having a stentbody, valve elements, and a cuff having a plurality of regions arrangedaround the circumference of the stent body. In an operative, implantedcondition, the regions of the cuff have differing radial thickness. Forexample, the cuff may include plural bulge regions separated from oneanother by intermediate regions having lesser radial thickness than thebulge regions. For example, a valve implanted in a generally triangularopening in a stenosed tricuspid arterial valve may have three bulgeregions. The bulge regions may be lodged in the corners of thetriangular opening. The various regions of the cuff may be provided withindividual inflatable chambers, so that bulge regions and intermediateregions can be formed as required for an individual patient.

Still other aspects of the invention provide methods of implanting avalve such as those discussed above, and kits for performing suchmethods.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may be more fully appreciated with reference tothe following detailed description, which in turn refers to thedrawings, wherein:

FIG. 1 is a schematic sectional representation of an aortic rootanatomy;

FIG. 2 is a perspective view of a portion of a stent body used in oneembodiment of the present invention;

FIG. 3 is a partial elevational view of a valve in accordance with oneembodiment of the present invention;

FIG. 4 is an end view of the valve depicted in FIG. 3;

FIG. 5 is a fragmentary, diagrammatic sectional view depicting portionsof the valve of FIGS. 3 and 4 in an implanted condition, in conjunctionwith portions of the native tissue;

FIG. 6 is a view similar to FIG. 5 depicting the valve of FIGS. 3 and 4in a different implanted condition;

FIG. 7 is a fragmentary, a diagrammatic elevational view of a portion avalve according to a further embodiment of the invention;

FIG. 8 is a fragmentary, diagrammatic perspective view depictingportions of a valve in accordance with yet another embodiment of thepresent the invention;

FIG. 9 is a diagrammatic perspective view of a valve according toanother embodiment of the invention;

FIG. 10 is a diagrammatic perspective view of a valve according to afurther embodiment of the invention;

FIG. 11 is a diagrammatic sectional view depicting portions of a valveaccording to yet another embodiment of the invention;

FIGS. 12A-D are fragmentary perspective views depicting elements of thevalve depicted in FIG. 11;

FIG. 13 is a diagrammatic perspective view of an element for use in afurther embodiment of the present invention;

FIG. 14 is a diagrammatic end view of a structure used in yet anotherembodiment of the present invention;

FIG. 15 is a partially sectional view of a valve according to yetanother embodiment of the present invention;

FIG. 16 is a view similar to FIG. 15 but depicting a valve according toa still further embodiment of the present invention;

FIG. 17 is a perspective view of a cuff for use in a valve according toa further embodiment of the present invention;

FIG. 18 is a perspective view of a valve incorporating the cuff of FIG.17;

FIG. 19 is a perspective view of another cuff for use in a valveaccording to yet another embodiment of the present invention;

FIG. 20 is a perspective view of a valve utilizing the cuff of FIG. 19;

FIG. 21 is an fragmentary diagrammatic elevational view of a collapsedconfiguration of a valve in accordance with a further embodiment of thepresent invention;

FIG. 22 is a diagrammatic view of the valve of FIG. 21 in a differentoperating condition;

FIG. 23 is a partially sectional diagrammatic view of a valve accordingto another embodiment of the present invention;

FIG. 24 is a fragmentary schematic view of a valve according to anotherembodiment of the present invention;

FIG. 25 is a partial, elevational, schematic view of a valve accordingto a still further embodiment of the present invention;

FIG. 26 is a schematic view of a valve according to an embodiment of thepresent invention in an implanted condition, in conjunction with nativetissue;

FIG. 27 is a fragmentary, diagrammatic, elevational view of a valve inaccordance with yet another embodiment of the present invention;

FIG. 28 is a schematic view of the valve of FIG. 27 in an implantedcondition, in conjunction with native tissue;

FIG. 29 is a fragmentary, diagrammatic, elevational view of a valveaccording to a still further embodiment of the present invention;

FIG. 30 is a fragmentary schematic view of a portion of the valve ofFIG. 30 in a different operating condition;

FIG. 31 is a schematic view of the valve of FIGS. 29 and 30 in animplanted condition, in conjunction with native tissue;

FIG. 32 is a view similar to FIG. 31 but depicting a valve according toa further embodiment of the present invention;

FIG. 33 is a fragmentary, diagrammatic sectional view depicting a valveaccording to yet another embodiment of the present invention; and

FIG. 34 is a partial, side, perspective view of a valve according to afurther embodiment of the present invention.

DETAILED DESCRIPTION

FIG. 1 is a simplified view of the geometry or anatomy of the aorticroot tissue in a typical human heart. The left ventricular outflow tract(LVOT) 1 communicates with the ascending aorta 5 through the annulus 2of the native aortic valve and the Valsalva sinus 3. The sinus joins theaorta at the sinotubular junction (STJ) 4. The native aortic valvetypically includes three native valve leaflets 6, of which only two arevisible in FIG. 1. As the left ventricle contracts during systole, bloodis forced from the LVOT 1 through the native valve and sinus and intothe aorta 5, moving generally in the downstream or antegrade flowdirection indicated by arrow D. Each native valve leaflet has aninterior surface 7 facing generally proximally and generally inwardly,toward the other native valve leaflets, and has an opposite-facingexterior surface 8. In a healthy individual, the native valve leaflets 6open away from one another and move to the position schematically shownin broken lines at 6′ to permit flow in this direction. During diastole,when the ventricle is not contracting, the native valve leaflets 6 moveback to the position indicated in solid lines in FIG. 1, where they abutone another or “coapt” so as to substantially block flow in the upstreamor retrograde direction, opposite to arrow D. The direction “distal” asused herein with reference to a feature of the native circulatory systemrefers to the direction of antegrade flow, i.e., the predominantdirection of blood flow through such feature, as indicated by arrow D.The direction “proximal” as used herein with reference to a feature ofthe native circulatory system is the opposite direction.

The parameters identified in FIG. 1 are as follows: DO=orifice diameter,i.e., the interior diameter of native annulus 2; DA=the diameter of theaorta just distal to the sinus; DB=maximum projected sinus diameter(this sinus is sometimes known as the Valsalva sinus); LA=length of thesinus, i.e., the dimension in the distal direction from the annulus 2 tothe sinotubular junction 4; and LB=distance in the distal directionbetween DO and DB.

The leaflets 6 have distal edges 9 remote from the annulus 2. Eachnative leaflet 6 has a surface 7, referred to herein as the “interior”surface of the leaflet, facing generally towards the other leaflets.Each native leaflet 6 also has a surface 8, referred to herein as the“exterior” surface of the leaflet, facing outwardly, away from the otherleaflets and toward the wall of the sinus 3. The cross sectional shapeof such a native valve varies somewhat from individual to individual,and this variation can be increased by various types of disease. Forexample, disease can reshape the cross section of a patient's valve to acircular, triangular, or elliptical shape, depending on the diseasestate.

An expandable stent body 10 (FIG. 2) for a prosthetic heart valve inaccordance with one embodiment of the present invention is formed as aunitary structure as, for example, by laser cutting or etching a tube ofa super elastic metal alloy such as a nickel-titanium alloy of the typesold under the designation NITINOL. Such a unitary structure can also bereferred to as a “non-woven” structure, in that it is not formed byweaving or winding one or more filaments. In the fully-expanded,unconstrained configuration depicted in FIG. 2, stent body 10 includesan annulus section 30, an aorta section 20 and support struts 60extending between the annulus section and the aorta section. The annulussection 30 in the expanded configuration is generally in the form of acylindrical tube having a central axis 14, whereas aorta section 20 isgenerally in the form of a hoop coaxial with the annulus section. In theexpanded configuration, the annulus section is of substantially constantdiameter except that the annulus section has a flared region 40 at oneend. The tubular annulus section 30 has a wall formed by numerous cellstruts interconnected to form a plurality of cells. The aorta section 20is defined by a similar wall formed of multiple cells, each of whichincludes a plurality of interconnected cell struts.

The stent body is adapted for installation in the body of a patient withthe annulus section adjacent the annulus 2 (FIG. 1) and with the aortasection 20 adjacent the sinotubular junction 4 and aorta 5. Thus, whenthe valve incorporating the stent body is placed in the patient, theaorta section 20 will be disposed distal to the annulus section 30 inthe frame of reference of the patient's circulatory system. Accordingly,as used with reference to features of the stent body and valve, thedirection D (FIG. 2) along axis 14 from the flared region 40 of theannulus section 30 through the annulus section and from the annulussection towards the aorta section 20 is referred to as the distaldirection, and the opposite direction is taken as the proximaldirection. Stated another way, the distal direction along the stent bodyis the direction from the end of the stent which is intended fordisposition at a proximal location in the frame of reference of thecirculatory system to the end of the stent which is intended fordisposition at a more distal location in the frame of reference of thecirculatory system. The “axial” directions as referred to herein are theproximal and distal directions. Also, the outward direction as used withreference to the valve is the direction away from the proximal-to-distalaxis 14. As used with reference to features of the valve, the“circumferential” directions are the directions around axis 14.

Stent body 10 includes features which facilitate attachment of valveleaflets as discussed further below. In this particular stent body, theleaflet attachment features include three commissure posts 50 formedintegrally with the remainder of the stent and extending axially in theannulus section 30. The commissure posts are connected to the cellstruts of the annulus section and are spaced equidistantly around theannulus section 30.

The particular construction of stent body 10 that is shown in FIG. 2(and subsequent figures) is only an example. Numerous other collapsibleand expandable stent bodies can be used. Merely by way of example, theannulus region may include multiple rows of cells; leaflet attachmentfeatures other than the axially-extensive posts can be used; and theaorta section 20 and struts 60 may be omitted. As one example, FIG. 33shows a stent variation with multiple rows of circumferentiallycollapsible/expandable cells in the annular valve section 30 of thestent body 10. Referring to FIG. 34, a few representative cells in themore distal or downstream row are numbered 32 a, while a fewrepresentative cells in the more proximal or upstream row are numbered32 b. The locations of some of the cells that are otherwise obscured bycuff material in FIG. 34 are enhanced by the addition of dotted lines.

A valve 100 (FIG. 3) incorporating a stent body 10 similar to thatdiscussed above with reference to FIG. 2 includes three flexibleprosthetic leaflets 70 formed from a biocompatible material such as ananimal tissue as, for example, pericardial tissue or a syntheticpolymeric material such as a silicone-polyurethane polymer. The leafletsare mounted to the stent body as, for example, by suturing the leafletsto posts 50, so that when the valve and stent body are in an expandedcondition as depicted in FIG. 3, the leaflets are disposed in whole orin part within the annulus section 30 of the stent body.

The valve also includes a cuff 85. The cuff includes a first cuffportion 80, also referred to herein as a supra-annular cuff portion,extending over a region of the tubular wall of the annulus section 30remote from the proximal end of the annulus section and distal to theflared region 40 of the annulus section. The cuff also includes a secondportion, also referred to herein as the sub-annular cuff portion 90,proximal to the first portion 80. A line 110 is shown in FIG. 3 as aboundary between these two cuff portions for clarity of illustration. Inactual practice, there may or may not be a visible demarcation betweenthese portions. Line 110 is approximately at the bottom of commissureposts 50. Stated another way, in this embodiment, the second cuffportion 90 is disposed proximal to the commissure posts and proximal tothe prosthetic leaflets 70. In the embodiment shown in FIG. 3, bothfirst cuff portion 80 and the second cuff portion 90 extend over theexterior surface of the stent body, i.e., the surface facing outwardlyaway from axis 14. The second or sub-annular cuff portion 90 alsoincludes a layer of material 120 (FIG. 4) on the interior surface of theflared portion 40 of the stent. Thus, the second or sub-annular portion90 of the cuff is thicker than the first or supra-annular portion 80. Abroken line 105 is shown in FIG. 4 for clarity of illustration at thejuncture of inner layer 120 and the layer on the exterior surface, i.e.,at the proximal edge of the stent body. In actual practice there may beno visible boundary at this location. In the particular embodimentdepicted in FIG. 4, the entire cuff 85 is formed from a unitary sheet ofmaterial. Layer 120 is integral with the cuff material on the exteriorof the stent, and is formed by folding the unitary sheet around theproximal edge of the stent. The material on the interior and exterior ofthe stent may be sutured together.

This particular embodiment is only illustrative; in other arrangements,the cuff portions 80 and 90 may be formed as separate pieces of the sameor different materials. Either or both cuff portions may include one ormore layers on the inside of the stent body, one or more layers on theoutside of the stent body, or both. The layers on the inside and outsideof the cuff may be formed separately from one another or integrally withone another. The cuff desirably is attached to the stent as, forexample, by suturing to the cell struts, to the junctures between thecell struts, or both. The cuff may be formed from materials such asanimal tissues as, for example, porcine, ovine and bovine pericardium,porcine sub-mucosa, and synthetic fabrics such as knit or wovenpolyester, and non-woven fabrics. Collagen-impregnated fabrics may beused. Also, bio-absorbable materials such as polyglactin, copolymers oflactide and caprolactone, and polylactides can be used.

FIG. 4 shows valve 100 (FIG. 3) as seen in axial view, looking distallyfrom the proximal end of the valve. The three flexible leaflets 70 canbe seen in FIG. 4 in their nearly closed condition (i.e., upper “free”edges of the leaflets coming together in approximately a Y pattern). Thevalve is preferably designed to close with fully redundant coaptationwhen under diastolic back-pressure.

In operation, the valve is brought to a collapsed condition and mountedon a delivery device (not shown) such as an elongated probe having asheath adapted to retain the stent body in the collapsed condition. Thedelivery device may include a mechanical or other arrangement forreleasing the stent body from the sheath once the valve has beenadvanced to the desired location within the body. For example, thedelivery device may be arranged to move the sheath with respect to thestent body in response to a manipulation by the operator. In thecollapsed condition, the stent body, including the annulus section 30and aorta section 20, is radially compressed. The prosthetic valveleaflets 70 are folded within the stent body. Because the thick secondor sub-annular portion 90 of the cuff is disposed proximal to the valveleaflets, it does not impede collapse of the valve to a relatively smalldiameter.

The delivery device is advanced into the patient's body until the valveis aligned with the native aortic valve, with the annulus section 30adjacent the annulus of the aorta. The valve is released from the sheathand stent body 10 expands under its own resilience. The resilientexpansion may occur solely as a result of release of mechanicalconstraint of the stent body, or may include expansion resulting fromthe effects of temperature change on the material of the stent body. Inthis embodiment, the entire expansion of the stent body from itscollapsed condition to its expanded, operative condition is broughtabout by the stent body itself. Stated another way, the stent bodydesirably is fully self-expanding and does not require a balloon ormechanical movement device to bring about any part of the expansion. Asbest seen in FIG. 5, the annulus section 30 brings the supra-annular orfirst section 80 of the cuff into engagement with the annulus 2 of thenative aortic valve, and into engagement with the interior surfaces 7 ofthe native valve leaflets. Expansion of the annulus section 30, andparticularly expansion of the flared portion 40, brings the second orsub-annular section 90 of the cuff into engagement with the LVOTproximal to the annulus 2. The cuff forms a seal with the nativeanatomy. Depending on the anatomy of the particular patient, the sealmay be formed with one or more of the interior surfaces 7 of the nativevalve leaflets, the annulus and the LVOT. The aorta section 20 (FIG. 1)engages the native anatomy at or near the sinotubular junction 4.

Although the stent reaches an expanded configuration, it typically doesnot reach its fully-expanded, unconstrained configuration. Thus, theresilience of the stent body typically causes the aortic section 20 tobear on the sinotubular junction and also causes the annulus section 30to bear on the annulus and on the interior surfaces of the leaflets,which helps to maintain the sealing engagement of the cuff with thenative anatomy. The prosthetic valve leaflets 70 open to allow distal orantegrade flow of blood during systole, and close to block proximal orretrograde flow during diastole. The sealing engagement of the cuff withthe native anatomy helps to block retrograde flow around the outside ofthe stent body, commonly referred to as perivalvular leakage. The valvedoes not block flow to the coronary arteries. For example, the supportstruts 60 may extend across the Valsalva sinus, so that blood can flowto the coronary arteries through spaces between the support struts.

FIG. 6 is similar to FIG. 5, but shows the valve used in an alternativeimplantation procedure. In this procedure, the patient's native aorticvalve leaflets have been resected (removed), typically prior toimplanting prosthetic valve 100 in the patient as shown. In thisembodiment as well, the first or supra-annular portion 80 of the cuff isengaged with the native valve annulus 2, whereas the second cuff portion90 is in contact with the native anatomy proximal to annulus 2, i.e.,with the distal end of the left ventricular outflow tract (LVOT).

The embodiment discussed above can be varied in many ways. For example,FIGS. 5 and 6 depict the cuff disposed only on the outside of theannulus region 30 and flare portion 40 of the stent body. However, thecuff may be disposed only on the inside or on both the inside andoutside. Also, the stent body may not be entirely or even partiallyself-expanding. The stent body may be brought from its collapsedcondition to an expanded, operative condition by one or more inflatableballoons or mechanical elements incorporated in the delivery device.

A valve according to a further embodiment includes a cuff 200 (FIG. 7)formed extending around the exterior of the annulus section 202 of thestent. In the radially expanded condition of the stent body, thematerial of the cuff is pleated. In this embodiment as well, the stentis a radially collapsible structure, and may be similar to the stentbody discussed above. For example, the annulus section may includenumerous cells which cooperatively define a tubular wall, each such cellbeing formed from interconnected cell struts 204. In the radiallycollapsed condition (not shown), the cell struts are oriented morenearly parallel to the proximal-to-distal axis 214 of the stent body.Thus, as the stent is transformed from the radially expanded conditiondepicted in FIG. 7 to the radially collapsed condition, the annulussection tends to elongate in the axial direction. In the reversetransition, from the radially collapsed condition to the radiallyexpanded condition, the annulus region decreases in axial length as itincreases in diameter. The pleats in the cuff define a plurality ofvalley regions 203 and ridge regions 205 extending generally in thecircumferential direction. As the stent decreases in axial length duringtransition to the radially expanded condition, the adjacent valleyregions move toward one another. This facilitates radial expansion ofthe ridge regions. Optionally, the cuff may be attached to the stentbody only in the valley regions. The pleats may or may not be present inthe radially collapsed condition of the stent body. Stated another way,the axial extension of the stent body during radial collapse maycollapse ridge regions 205 inwardly to the same diameter as the valleyregions 203. In the radially expanded condition of the stent body, thepleats help to form an effective seal with the native tissue. Pleatedcuffs according to this embodiment may be formed from the cuff materialsdiscussed above. The pleats need not be exactly circumferential. Forexample, there may be one or more helical valley regions and one or morehelical ridge regions, so that the valley and ridge regionscooperatively define a form generally like a screw thread.

The valve of FIG. 7 also includes biasing elements in the form of bands210 of hygroscopic, sponge-like material that collapses easily and fillsto a larger volume when the stent is expanded after implantation. Merelyby way of example, the hygroscopic material may be a collagen foam orsponge similar to the material commercially available under thetrademark Angioseal which is used to plug arteries, and to the similarmaterial currently used for embolic protection. The biasing elements orbands 210 are formed separately from the cuff and are engaged betweenthe ridge regions 205 of the cuff and the exterior surface of theannulus portion 202 of the stent. Thus, the biasing elements aremechanically engaged with the cuff and stent body. When the valve isimplanted and the material of bands 210 swells, the biasing elementsurge the ridge regions of the cuff outwardly with respect to the annulusregion 202 of the stent body. In the embodiment of FIG. 7, the bands ofhygroscopic material are disposed proximal to the prosthetic valveleaflets 271, and hence are axially offset from the leaflets. Thisfacilitates collapse of the valve to a small diameter. In a valveaccording to yet another embodiment (FIG. 8), the biasing elementincludes a helical band 211 of hygroscopic material disposed inside thecuff 201.

Biasing elements such as hygroscopic material can be used with cuffsother than the pleated cuffs shown in FIGS. 7 and 8. Bands ofhygroscopic material can be integrated into the valve to take advantageof specific geometry in order to increase the sealing ability thereof,while not compromising (i.e., unduly increasing) the collapsed valvediameter. For example, in a valve which includes a cuff having asub-annular portion as discussed above with reference to FIGS. 3 and 4,the biasing element can be located to expand the sub-annular cuffportion (i.e., on the upstream side of the patient's native valveannulus). Here again, because the biasing element is axially offset fromthe prosthetic valve elements, it does not add to the cross section ofthe prosthetic valve where the leaflets are when the valve is collapsed.In the collapsed condition, the bulk of the biasing element is notsuperimposed on the bulk of the leaflets. This helps make it possible tocollapse the valve to a smaller circumferential size than would bepossible if both the leaflets and biasing element were in the same crosssectional area of the valve.

In a further variant, a biasing element such as a water-absorbingpolymer may be placed between layers of cuff material, so that thebiasing element will urge the outer layer away from the stent body. In afurther embodiment, the cuff material may be impregnated with such apolymer. When allowed to expand as a result of implantation in a patientand consequent absorption of water from the patient's tissue and/orblood, these materials can fill any gaps in the cuff material and canalso fill gaps between the cuff material and the native tissue to reducePV leakage.

Staples and/or sutures can be used to secure the valve to the patient'snative valve annulus using elongated instruments introducedtrans-apically or percutaneously. The valve depicted in FIG. 9 has astent body which has an annulus section 30 similar to the annulussection of the valve discussed above with reference to FIGS. 2-4. Thisparticular valve body does not have an aortic section as used in thevalve body of FIGS. 2-4. The annulus section 30 has a flared portion(not shown) at its proximal end, i.e., at the bottom of the drawing asseen in FIG. 9. In this embodiment as well, the cuff includes a secondor sub-annular cuff portion 90. Cuff portion 90 can be sutured orstapled to the patient's native tissue because the bases or proximaledges of the prosthetic valve leaflets 70 are downstream from cuffportion 90. Dotted lines 72 in FIG. 9 indicate the approximate locationsof the leaflet bases. Areas 92 of the second cuff portion 90 are thusavailable for stapling or suturing through cuff 90 into the patient'snative tissue without interfering with prosthetic leaflets 70.

The valve of FIG. 10 includes a cuff 285 defining multiple pockets 220.Each cuff has an open side facing in the distal direction. The othersides of each cuff are substantially closed. When the valve isimplanted, these pockets will impede perivalvular leakage or retrogradeblood flow around the outside of the stent body. Retrograde flow willtend to fill each pocket with blood and thus bias the outer surface ofthe pocket outwardly, into engagement with the native tissue as, forexample, into engagement with the annulus or native valve leaflets.Stated another way, the pockets act like miniature parachutes around theperiphery of the valve. It is expected that pockets 220 will eventuallyhave tissue ingrowth to eliminate the long-term need for their PV leakprevention function. In FIG. 10 the mini-pockets 220 of the cuff areconstructed to impede retrograde flow. It will be appreciated, however,that the pockets can be oriented in the opposite direction (i.e., toprevent forward blood flow), with their open sides facing generallyproximally. The pockets can be provided in any number, size, and/orshape to minimize leakage. Pockets 220 can be made of the same cuffmaterials as discussed above.

A valve according to a further embodiment of the invention (FIG. 11)incorporates biasing elements in the form of springs 230 formedintegrally with the stent body. In the expanded condition of the stentbody, portions of the springs project outwardly from the tubular wall ofthe annulus section 30. The cuff, or the outermost layer of the cuff, isdisposed outward of the tubular wall and outward of the springs, so thatthe springs tend to bias the cuff 85 outwardly with respect to the wallof the annulus section. Biasing elements of this type can be provided atany location along the cuff. The springs 230 may be axially-extensivefingers as depicted in FIG. 12, or may have other configurations. Forexample, springs in the form of fingers may be directed generallycircumferentially. The fingers may have blunt ends for engagement withthe cuff, as depicted at 230 c and 230 d in FIGS. 12C and 12D,respectively. Alternatively, the fingers may have sharp ends as depictedin FIGS. 12A and 12B, respectively, at 230 a and 230 b. Fingers withsharp ends may pierce the cuff and also may pierce the native tissue.

The biasing elements may also include coil springs. As shown in FIG. 13,a conical coil spring 252 has a spring axis 250 and a spring memberdisposed in a helix around the spring axis so that the spring memberdefines a plurality of turns of progressively increasing diameter. Thelargest turn 253 defines a base surface of the spring. A plurality ofsuch springs can be mounted between the stent body and the cuff, withthe base surface facing inwardly toward the stent body, and with thespring axis extending generally in a radial or outward direction. Hereagain, the spring will tend to bias the cuff outwardly with respect tothe stent body. Where the stent includes cells formed from cell struts,the base surface of each spring may bear on a juncture between struts.Also, where the stent includes commissure posts, such as the posts 50depicted in FIG. 2, the springs may bear on the commissure posts. In afurther arrangement, springs may be provided between layers of amulti-layer cuff. Each spring 252 can be cut from a flat sheet in a coil(spiral) pattern and shaped into a cone. The material can be ashape-memory/super-elastic material such as Nitinol. Depending on thesize of the base of the spring, each turn of the spiral could even besaddle-shaped to enable the spring to conform to the curvature of theportion of the stent that the spring is sitting on (FIG. 14).

In a further embodiment (FIG. 14), the turns 251 are generallyelliptical as seen in end view, looking along the spring axis 250. Also,in this embodiment, the base surface defined by the largest turn 253 iscurved around an axis 257 transverse to the spring axis 250. Thus,portions 255 of turn 253 remote from axis 257 project in directionsparallel to the spring axis 250, out of the plane of the drawing, towardthe viewer as seen in FIG. 14. The other turns desirably have a similarcurvature. Thus, when the spring is fully collapsed, it has the shape ofa portion of a cylinder, with axis 257 being the axis of the cylinder. Aspring according to this embodiment may be mounted to the stent body,with the transverse axis 257 oriented generally parallel to the axis ofthe cylindrical surface, and desirably coaxial with such cylindricalsurface. Stated another way, the spring in its collapsed or compressedcondition may match the curvature of the stent body in its radiallycollapsed condition. This design has the ability to be low-profile, withminimum radial extent when collapsed, and the ability to push radiallyoutwardly when deployed.

Coil springs as shown in FIGS. 13 and 14 can be cut from a flat sheet,and then heat set or formed on mandrels to make them obtain thecharacteristics of a spring. They can be attached by means of sutures,welds, locking mechanisms, etc. to the stent body or placed within theappropriate cuff portion. The coil springs also may be formed integrallywith the stent body.

A valve according to yet another embodiment of the invention, shown inFIG. 15, includes a cuff 85 similar to the cuffs discussed above.However, in this embodiment, the cuff is provided with a thin ring 260formed from a resilient material such as silicone rubber. Ring 260extends circumferentially around the remainder of the cuff and aroundthe annulus section 30 of the stent body. The ring has a main portion261 bearing on the stent body through the other layers of the cuff, andhas a free edge 262 axially offset from the main portion. When the stentbody is in its radially collapsed condition, the free edge of the ringlies flat against the other structures of the stent. When the internaldiameter of the ring is forcibly expanded by transition of the annulussection 30 of the stent body, the free edge 262 of the ring tends toflip up and thus tends to project outwardly relative to the main portion261 and relative to the stent body. This causes the free edge 262 of thering to seal against the surrounding native tissue, even where thenative tissue is irregular. The ring has a low enough profile to becollapsed during delivery of the prosthetic valve into the patient. Thering can be placed anywhere along the axial extent of the annulussection. If it is axially offset from the prosthetic valve leaflets 70,as by placing it in the area of the second sub-annular cuff portion 90,this will minimize the material of the valve in the cross section of theleaflets.

A ring such as that discussed above with reference to FIG. 15 also canbe used as a biasing element, so as to bias another portion of the cuffoutwardly with respect to the stent body. For example, in the embodimentof FIG. 16, a ring 260 similar to that discussed above is disposedbetween the stent body and an overlying portion 270 of cuff material.The free edge of the ring bears on this portion 270 and urges itoutwardly with respect to the stent body. The cuff bulge 210 shown inFIG. 16 is thus caused by the free edge of the silicone ring flippingup.

Because the features as discussed above with reference to FIGS. 7-16provide an outward bias to portions of the cuff, they tend to promoteeffective sealing between the cuff and the surrounding native tissueeven where the native tissue is irregular. While these features havebeen discussed above in connection with an expansible stent body, theycan be used with other types of stents. For example, a valve intendedfor implantation in an open surgical technique may include anon-expandable, substantially rigid stent. The biasing features may beemployed with stents of this type as well.

The calcific patterns of aortic stenosis can occur in a variety ofdistribution patterns, which can have a direct effect on PV leak betweenthe stenotic leaflets and an implanted collapsible valve. In many cases,PV leak is most likely to occur at the location of the commissuresbetween the stenotic native leaflets (R. Zegdi et al., “Is It Reasonableto Treat All Calcified Stenotic Aortic Valves With a Valved Stent?”,Valvular Heart Disease, Vol. 51, No. 5, pp. 579-84, Feb. 5, 2008).Stated another way, the native valve annulus, and the space defined bythe interior surfaces of the native valve leaflets, do not have acircular cross-sectional shape. A valve according to a furtherembodiment includes a cuff 285 (FIG. 17) which includes a plurality ofregions 280 distributed around the circumference of the cuff. In theoperative, implanted configuration shown, some of these regions 280 a,280 b and 280 c, referred to herein as “bulge” regions, have a radialthickness R greater than the radial thickness of other regions, such asregions 280 d, 280 e and 280 f, referred to herein as “intermediate”regions. In the particular example of FIGS. 17 and 18, there are threebulge regions spaced circumferentially from one another and intermediateregions between the bulge regions. In another example, shown in FIGS. 19and 20, there are two bulge regions 280 a and 280 b spaced from oneanother and intermediate regions such as 280 e and 280 d between thebulge regions. The number and location of the bulge regions desirably isselected to match the configuration of the native tissue of theparticular patient. Therefore, in order to tailor the valve cuffspecifically to a particular patient, each region 280 incorporates aseparate chamber 287 (FIG. 18). Each chamber can be inflated to providea bulge region or left deflated to provide an intermediate region. Thisarrangement can provide sufficient sealing against PV leak withoutadding additional, unnecessary cuff material. The configuration of FIGS.17 and 18 can be used, for example, in a patient having a typicaltricuspid native aortic valve with stenotic native leaflets. Theconfiguration of FIGS. 19 and 20 can be used in a patient having astenotic bicuspid native aortic valve.

The chambers can be inflated either before implantation or after thevalve has been expanded into the stenotic native valve. Inflation can beachieved intra-procedurally with material such as liquid collagen or RTVsilicone, or prior to the procedure with similar or other materials.This cuff construction offers the potential for a single collapsiblevalve design to be used in a variety of stenotic aortic valve sizes andcalcific distribution patterns, whereas some of the previously knowndesigns can only be used with uniform calcific distribution patterns.This cuff design may also be used in aortic insufficient (leaking)valves because of its ability to fill PV-leaks and gaps. Other possibleuses of this cuff design are in other valve positions. For example, aconfiguration such as that shown in FIGS. 19 and 20 may be particularlywell suited for the mitral valve, which is naturally elliptical andoften insufficient (leaking).

As further discussed below, certain techniques which can be employed inprosthetic heart valve procedures may best be applied while the regionstreated by these techniques are temporarily isolated from direct bloodflow. A device that isolates a working chamber may be beneficial. Onesuch device is disclosed in R. Quaden et al., “Percutaneous Aortic ValveReplacement: Resection Before Implantation,” European Journal ofCardio-thoracic Surgery, Vol. 27, 2005, pp. 836-40, the disclosure ofwhich is hereby incorporated by reference herein. As disclosed in theQuaden et al. article, an aortic valve resection chamber is sealed bypolyethylene balloons. The surgical instruments are inserted through aninstrument channel. Two catheters with small sealing balloons providethe coronaries with cardioplegia and prevent coronary embolizationduring the resection process. A working chamber of this type may also bebeneficial (although not necessary in all cases) for application of sometechniques such as those described later in this specification.

Lasers have long been used to coagulate tissue in the medical industry.An example is the Laserscope system used for cauterizing tissue(available from Laserscope, 3052 Orchard Drive, San Jose, Calif.95134-2011). A low power laser that can minimize tissue vaporization,yet bond tissue together, is optimal. Other energy sources such asultrasound, cryogenics, an electrical resistance or other heatingelement can be used as alternatives. The cuff of a prosthetic valve canbe made to be bonded to native tissue as, for example, to the stenoticleaflets (or to the native valve annulus if leaflets are resected)during or after implantation. For example, a porcine pericardial stripon the outside of the cuff can be used to bond a tissue-to-tissue joint.Probes of various shapes (toroid, pointed, etc.) can be used todirectionally apply the energy to the desired locations.

Biocompatible adhesives, such as epoxy amines, have been applied incertain medical applications. (See, for example, U.S. Pat. Nos.6,780,510 and 6,468,660.) Such adhesives can be applied around theperimeter of the cuff of a prosthetic valve to bond to stenotic leaflets(or annulus if leaflets are resected) during or after implantation.Other silicone materials can be used as a “caulk” in certain situations.The adhesive can be injected internally or externally through ports inthe valve cuff itself and/or the cuff can have pockets to allow forinjection (see FIGS. 10, 12, and 16.

A valve according to a further embodiment of the invention (FIG. 21)includes an expandable stent body 10 having an annulus section 30 with aproximal-to-distal axis 14. The valve also includes a cuff 400 having agenerally tubular wall with a free end 402 and with surfaces 403 and404. In the collapsed condition shown, surface 403 is the inner surfaceof the tube and surface 404 is the outer surface. In the radiallycollapsed condition of the stent body 10, the tubular wall projects fromthe proximal end of the stent so that the free end 402 of the tubularwall is proximal to the annulus section 30. Stated another way, in thiscondition, the free end 402 of the tubular wall is axially offset fromthe annulus section and is axially offset from the stent body. Thus FIG.21 shows crimped or collapsed stent 30 and crimped or collapsed cuff 400at different, substantially non-overlapping locations along theproximal-to-distal axis of the valve. Elements 30 and 400 may beconnected to one another, e.g., at an interface between them. But theypreferably do not overlap, at least not to a great extent. Thus, in thiscondition the thickness of the tubular wall 400 does not add to thediameter of the stent. This is desirable for keeping the outer diameter,and hence the circumferential size of the valve, as small as possiblefor less invasive delivery into the patient.

FIG. 22 shows the structure of FIG. 21 when implanted in the patient. Inparticular, FIG. 22 shows annulus section 30 in a radially expandedcondition. Cuff 400 is also radially expanded and has been flipped up orturned inside-out (everted) so that it is now disposed around theoutside of at least a portion of the annulus section 30 of the stentbody. Note that surface 403 is now on the outside of the tube. Inconversion from the collapsed condition to the operative condition, thefree end 402 of the tube moves with respect to the stent body.Accordingly, the free end 402 is referred to herein as a “mobile”portion of the cuff. In the operative condition depicted in FIG. 22, thefree end or mobile portion is axially aligned with part of the annulussection 30. In this condition cuff 400 helps ensure proper sealing ofthe valve to the patient's surrounding native tissue.

Tubular cuff 400 can be flipped up during delivery of the valve into thepatient but before the valve is fully seated at the valve implant sitein the patient. Depending upon the resilient properties of the tubularcuff 400, radial expansion of the stent body may cause the tubular cuffto evert as shown. Alternatively or additionally, the tubular cuff mayhave a free or undistorted shape such that it naturally tends to evertas shown in FIG. 22 when unconstrained. The tubular cuff may be forciblydistorted to the condition depicted in FIG. 21, and constrained in thatposition by a sheath or other element of a delivery device. Thus, asshown in FIG. 23, after cuff 400 has emerged from the distal end of adelivery sheath 500, the cuff tends to resiliently flip up around theoutside of stent body 10. FIG. 24 shows an alternative or addition inwhich sutures or wires 510 are used to pull the mobile element or end402 of cuff 400 up and around the outside of stent body 10. Thismovement may be performed before, during, or after expansion of thestent body. Merely by way of example, where the delivery device includesan elongated probe, the sutures or wires 510 may extend along thedelivery device to a handle or other element accessible to the operator.Also, the sutures may be provided as loops which can be removed from thecuff by selectively pulling one end of the loop. For example, sutures510 a and 510 b are parts of a unitary loop extending through holes inthe cuff. Pulling both ends of the loop simultaneously tends to pull thefree edge or mobile portion 402. Pulling one end of the loop will removethe suture from the cuff. FIG. 25 shows still another alternative oraddition in which shape-memory alloy (e.g., nitinol) members 410 in oron cuff 400 cause the cuff to flip up when the cuff is released fromdelivery system constraint inside the patient at or near the valveimplant site.

A cuff with a mobile portion may be arranged to form a seal with anyportion of the native anatomy. For example, FIG. 26 shows a prostheticvalve fully implanted in a patient, with cuff 400 flipped up around theoutside of stent body 10 and pressed radially outwardly against thepatient's native, stenotic, heart valve leaflets 6 to seal theprosthetic valve against PV leak.

FIG. 27 is generally like FIG. 21, but in FIG. 27, cuff 400 is longerthan in FIG. 21. FIG. 28 is generally like FIG. 23, but shows the FIG.27 structure after it has been implanted in a patient. In the structureof FIGS. 27 and 28, cuff 400 has an axial extent that is about the sameas the axial extent of the annulus portion 30 of the stent body. In thisembodiment, the proximal end of the stent may be disposed proximal tothe native valve annulus 2, and yet a portion of cuff 400 will stillreach and seal against native structures such as annulus 2 and stenoticleaflets 6. The structure of FIGS. 27 and 28 incorporates a balloondisposed on the delivery device inside the stent body, such as withinthe annulus region 30 of the stent body, for forcibly expanding thestent body. This structure also includes a further balloon which isdisposed within the cuff when the stent is in the radially collapsedcondition. The cuff 400 can be turned inside-out by inflating the secondballoon before or during expansion of the stent body. In furthervariants, the balloon may be arranged to expand progressively, beginningat the free end 402, to help turn the cuff inside out. Merely by way ofexample, such balloon may include a plurality of chambers disposed alongthe axis of the structure, so that these chambers can be inflated insequence.

In other embodiments, the mobile portion of the cuff may be movedrelative to the stent body by engagement with native anatomicalstructures. For example, the cuff can be constructed and delivered sothat it latches on the patient's native stenotic heart valve leafletsduring delivery. FIGS. 29-31 show one examples of this action. The valveof FIG. 29 is generally similar to the valves of FIGS. 21 and 27, butshows the addition of engagement elements in the form of hooks 420 onthe free end 402 of cuff 400 remote from stent 30. FIG. 30 shows thestructure of FIG. 29 in a stage of deployment. In this stage, thetubular cuff has deformed to a configuration where the latch members orhooks 420 can engage (latch onto) the distal edges of the patient'snative stenotic leaflets 6. Once the latch members have been engaged,the stent body is moved in the proximal direction relative to the nativeanatomy. As shown in FIG. 31, the proximal movement of stent body 10into the space bounded by native leaflets 6 causes cuff 400 to evertaround the outside of stent 10. This is aided by the fact that hooks 420secure the free end 402 of cuff 400 to the distal edges of leaflets 6.Ultimately (as shown in FIG. 31), cuff 400 is sandwiched between stentbody 10 and native leaflets 6. The presence of hooks 420 over nativeleaflets 6 helps cuff 400 seal the prosthetic valve against PV leak, andalso helps to anchor the valve in place in the patient.

The engagement elements or hooks 420 can be of any suitable material.One possibility is for hooks 420 to be made of nitinol and to extendthrough the fabric or other material of cuff 400. Hooks 420 may beconnected to the annulus section 30 or other portions of the stent body,and may be formed integrally with the stent body.

In the procedure of FIGS. 29-31, the mobile element is moved duringproximal movement of the valve, from the aorta 5 towards the leftventricle 1. In a further variant, the mobile element is deployed bymovement in the opposite, distal direction relative to the nativeanatomy. In such a case, hooks 420′ can be arranged to latch intoannulus 2 as shown in FIG. 32. In this arrangement, the tubular cuffelement initially projects from the distal end of the annulus section30. The latch members 420′ engage native anatomical structures such asthe LVOT. The free end or mobile element moves proximally with respectto the annulus section 30 of the stent body as the stent body movesdistally relative to the native anatomy.

The mobile portion of the cuff may include the entire cuff or any partof the cuff. Also, motion of the mobile portion of the cuff can occur inways other than turning the cuff inside out. For example, the structureof FIG. 33 incorporates a cuff 400 and a stent body 10 having an annulusregion 30. During advancement of the valve into the patient, the stentis constrained in its radially collapsed condition by a sheath 605. Thecuff 400 includes a resilient tube having an unconstrained internaldiameter approximately equal to, or greater than the external diameterof the annulus region 30 in its radially collapsed condition. Duringadvancement into the patient, the cuff is retained in a collapsedcondition by a further sheath 607 separate from sheath 605. Duringdeployment, sheath 607 is moved in axial direction A1 relative to sheath605, so as to free at least the part of cuff 400 closest to the stentbody and allow it to expand. While moving sheath 605 axially indirection A2 relative to the stent body, the cuff is also moved axiallyrelative to the stent body before the stent body expands fully to itsoperative, radially expanded state. For example, the delivery device mayinclude sutures 510 similar to those discussed above with reference toFIG. 24 for moving the cuff. As the stent body expands, it engages theinside of the cuff. Where the stent body is forcibly expanded by aballoon or mechanical element, the cuff can be slipped over the exteriorof the stent body so as to pull the cuff around the outside of the stentbody before or during operation of the expansion device.

Although the valves have been discussed above with reference toimplantation of the valves in naturally-occuring native valves of apatient, the valves also can be implanted within previously-implantedprosthetic valves. In such a procedure, the previously-implantedprosthetic valve constitutes the native valve. For example, the cuffwill seal against structures of the previously-implanted prostheticvalve as, for example, against the interior of the previously-implantedstent body and cuff, or the interior surfaces of previously-implantedprosthetic valve leaflets.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

1. (canceled)
 2. A prosthetic heart valve, comprising: (a) a stent thatis collapsible for mounting on a delivery device; (b) a valve elementmounted within the stent; and (c) a cuff around the periphery of thestent, the cuff including at least one pocket sized, shaped andpositioned on the stent for engagement within the native valve annulusto impede perivalvular leakage.
 3. The prosthetic heart valve accordingto claim 2, wherein the stent includes a downstream collapsible andexpandable ring portion and an upstream collapsible and expandable ringportion that is annularly expandable within the native valve annulus. 4.The prosthetic heart valve according to claim 3, wherein the cuff isdisposed around the upstream ring portion.
 5. The prosthetic heart valveaccording to claim 3, wherein the upstream ring portion includes aflared region.
 6. The prosthetic heart valve according to claim 2,wherein the at least one pocket has an outer surface that is biasedoutwardly into engagement with the native valve annulus by retrogradeblood flow.
 7. The prosthetic heart valve according to claim 2, whereinthe at least one pocket has an outer surface that is biased outwardlyinto engagement with the native valve annulus by antegrade blood flow.8. The prosthetic heart valve according to claim 2, wherein the cuffincludes a plurality of pockets.
 9. The prosthetic heart valve accordingto claim 2, wherein the stent is self-expanding.
 10. The prostheticheart valve according to claim 2, wherein the stent is balloonexpandable.
 11. An assembly for delivering a prosthetic heart valve to atarget site in a patient, comprising: (a) a delivery device having aretractable sheath; and (b) a prosthetic heart valve mounted on thedelivery device and covered by the sheath, the prosthetic heart valveincluding a collapsible and expandable stent, a valve element mountedwithin the stent, and a cuff around the periphery of the stent, the cuffincluding at least one pocket sized, shaped and positioned on the stentfor engagement within the native annulus to impede perivalvular leakage.12. The assembly according to claim 11, wherein the at least one pockethas an open side adapted to face in a direction of antegrade blood flow,the pocket being sized and shaped to impede perivalvular leakage aroundthe outside of the stent.
 13. The assembly according to claim 11,wherein the at least one pocket has an open side adapted to face in adirection of retrograde blood flow, the pocket being sized and shaped toimpede perivalvular leakage around the outside of the stent.
 14. Theassembly according to claim 11, wherein the delivery device includes anexpandable member for moving the stent from a collapsed condition to anexpanded condition.
 15. The assembly according to claim 14, wherein theexpandable member is a balloon.
 16. A prosthetic heart valve,comprising: (a) a stent that is collapsible for mounting on a deliverydevice having a sheath for covering the stent; (b) a valve elementmounted within the stent; and (c) a cuff around the periphery of thestent, the cuff including at least one pocket having an outer surface,the pocket being sized and shaped to fill with blood by blood flowaround the stent to bias the outer surface outwardly into engagementwithin the valve annulus.
 17. The prosthetic heart valve according toclaim 16, wherein the stent includes a downstream collapsible andexpandable ring portion and an upstream collapsible and expandable ringportion that is annularly expandable within the native valve annulus.18. The prosthetic heart valve according to claim 17, wherein the cuffis disposed around the upstream ring portion.
 19. The prosthetic heartvalve according to claim 17, wherein the upstream ring portion includesa flared region.
 20. The prosthetic heart valve according to claim 16,wherein the at least one pocket has an open side adapted to face in adirection of antegrade blood flow, the pocket being sized and shaped toimpede perivalvular leakage around the outside of the stent.
 21. Theprosthetic heart valve according to claim 16, wherein the at least onepocket has an open side adapted to face in a direction of retrogradeblood flow, the pocket being sized and shaped to impede perivalvularleakage around the outside of the stent.
 22. The prosthetic heart valveaccording to claims 16, wherein the stent is self-expanding.
 23. Theprosthetic heart valve according to claim 16, wherein the stent isballoon expandable.
 24. An assembly for delivering a prosthetic heartvalve to a target site in a patient, comprising: (a) a delivery device;and (b) a prosthetic heart valve mounted on the delivery device, theprosthetic heart valve including a stent, a valve element mounted withinthe stent, and a cuff around the periphery of the stent, the cuffincluding at least one pocket having an outer surface, the pocket beingsized and shaped to fill with blood by blood flow around the stent tobias the outer surface outwardly into engagement within the valveannulus.
 25. The assembly according to claim 24, wherein the pocket hasan open side adapted to face in a direction of antegrade blood flow, thepocket being sized and shaped to impede perivalvular leakage around theoutside of the stent.
 26. The assembly according to claim 24, whereinthe pocket has an open side adapted to face in a direction of retrogradeblood flow, the pocket being sized and shaped to impede perivalvularleakage around the outside of the stent.
 27. The assembly according toclaim 24, wherein the delivery device includes an expandable member formoving the stent from a collapsed condition to an expanded condition.28. The assembly according to claim 27, wherein the expandable member isa balloon.
 29. The assembly according to claim 24, wherein the deliverydevice includes a retractable sheath, and the prosthetic heart valve iscovered by the sheath.